1. Field
Embodiments of the present invention relate to a control device for a hybrid vehicle and a control method for a hybrid vehicle.
2. Description of the Related Art
A hybrid vehicle includes an engine, a motor generator, an inverter for driving the motor generator, and an electricity storage device, which charges and discharges power to and from the motor generator via the inverter.
Here, as a type of hybrid vehicle, there is a direct coupling type which mechanically couples an engine to a motor driving system. The motor driving system is configured with the motor generator and a belt and a pulley which transfer a driving force of the motor generator to an engine driving shaft.
In the direct coupling type hybrid vehicle, which mechanically couples the engine to the motor driving system, a loss, such as an iron loss, occurs from the motor generator at the time of an engine driving mode using only the driving force of the engine, that is, a drag torque in a deceleration direction against an engine output occurs.
As such, there are methods of generating a torque for removing the drag torque of the motor generator and methods of controlling the drag torque of the motor generator to a zero torque so that the drag torque of the motor generator does not hinder the engine output.
However, even in the case of mechanical elements such as the belt or the pulley that are part of the motor driving system, a rolling resistance, that is, a mechanical output (e.g., load) in the deceleration direction against the engine output, occurs.
Therefore, even though a zero torque control is performed to remove the drag torque of the motor generator, the overall motor driving system generates an output in the deceleration direction against the engine output and therefore may apply a load to the engine.